with polls now showing president obama building a lead over mitt romney in key battleground states, a democratic pollster and consultant who worked for jimmy carter says finding the right sample to survey can be tricky. >> we know from the exit polls and others, the republicans tend to respond to these polls less than oftentimes, particularly from news organizations, less than do democrats. >> in 1988, george bush managed a huge swing. gallup had michael dukakis leading by 17 points after the democratic convention, but lost to bush by 7.5%. in 1992, the incumbent president was down nine points in mid-september, tied with bill clinton by the end of october, though clinton eventually won. a former clinton pollster is questioning the assumptions being made in today's polls. >> these polls are assuming that you have the same high level of african american, latino, and young people vote in 2012 that you had in 2008. >> obama campaign senior advisor david axelrod told fox, "public polls are widely variant in their sampling and methodology so it's hard to case when they all point in one dire